Avalon Scrub Hairstreak
Looking very much like a faded and smaller gray hairstreak, this Catalina Island butterfly is a full species that doesn't occur anywhere else. For a species to be limited to a single island is very unusual. It apparently flies in two or more broods, and uses both deerweed (Acmispon glaber) and silver birds foot trefoil (Acmispon argophyllus) in the Fabaceae family. Smart move, as they are common plants.
This is Strymon avalona, the Avalon scrub hairstreak, which is found only on Santa Catalina Island. May 19, 2013.
Another Strymon avalona from the same trip. These were found along a dirt road above Two Harbors, which is on the northeast part of the Island. Santa Catalina Island is about 26 miles from the shore in Long Beach.
The dorsal of Strymon avalona, showing what must be structural coloration.
William G. Wright described avalona in his 1905 book, The Butterflies of the West Coast of the United States.